Retort pouches or microwaveable pouches are a flexible or semi-rigid package made from heat-resistant laminated plastic, into which food products are placed, sealed and sterilized at temperatures up to 121°C. The resulting product is then sterile and shelf-stable. The retort pouch has been developed as an alternative to metal and glass for packaging of processed food products. Retort pouches are used in several countries for a wide range of processed ready-to-serve shelf-stable muscle-based products, such as solid meat packs, beef curry or stew, meatballs in tomato sauce, sauces and soups etc.
Laminate films used for retort pouch manufacture vary depending upon their specific application. The materials must be inert, heat sealable, dimensionally stable and heat resistant (usually 115°C–125°C). They should have low oxygen and water-vapour permeability and be physically strong to resist penetration by the foodstuff contained and abuse during handling and storage.
There are two main types of pouches: gusseted and pillow packs. Pouches are made from either aluminium foil-based plastic laminates or foil-free plastic laminate films, which are suitable for microwave heating. Most pouches are either three- or four-ply (layer) laminates with an inner food contact heat-seal layer. Adhesives with a polyurethane-base between the layers of film hold the laminates together. The outer polyester layer is heat resistant and provides an area for logo printing, often reverse printing. In aluminium foil-free pouches the product is visible and microwaveable.
